....
fseek(arq, 0, SEEK_END);
while(!feof(arq)){
//fgets(&ch,2,arq);
fread(&ch, sizeof(char), 1, arq);
//printf("\n%c",ch);
num = atoi(&ch);
vem=makenode();
vem->numero=num;
lista=insertfirst(lista,vem);
}
....
How do I read from the end of the file to the start
For the record, I see this as something purely funny and with no real application, yet you can do it by using fseek and ftell .
It begins by positioning itself at the end with fseek and with ftell finds the position of that end. Then it decreases the position manually and uses fseek again to read from that byte:
int main(){
FILE *arq = fopen("teste.txt","r");
fseek(arq, 0, SEEK_END); //ir para o fim do arquivo
long posicao = ftell(arq); //assumir a posição como fim
char ch;
while(posicao >= 0){
fseek(arq, posicao, SEEK_SET); //reposicionar de acordo com a posicao
fread(&ch, sizeof(char), 1, arq); //ler o caratere
printf("%c\n",ch);
posicao--; //andar uma posição para trás
}
return 0;
}
The focus statement is:
fseek(arq, posicao, SEEK_SET); // arquivo, offset, tipo de posicionamento
SEEK_SET means positioning at startup. In this case, posicao bytes will be positioned from the beginning. As posicao decreases from 1 to 1 to while , it is increasingly positioning itself to the beginning.
A more performative solution is to read the whole file (start to finish) to a char[] and then use that array backwards, which avoids having to do multiple fseek s. p>